(a) Field of the Invention
The present invention concerns breathing apparatuses for scuba diving of the closed or semi-closed circuit type comprising a chamber of variable capacity, which is partially delimited by means of a movable wall which is mounted on a housing through its periphery, the chamber of variable capacity permanently communicating with a portion of an inhaling circuit and a portion of an exhaling circuit and, selectively, with a source of a gas under pressure, through a pressure reducer which is mounted on the housing and which is controllable by cooperation with the movable wall.
(b) Description of Prior Art
In breathing apparatuses of this type, the movable wall of the variable capacity chamber, commonly called "breathing bag" or "false lung", is normally made of a cloth of coated fabric intentionally made sufficiently rigid to artificially "stiffen" during the inhaling and exhaling of gas under pressure. This is relatively important to the respiratory work of the diver, even when the pressure reducer is not acted upon. As a matter of fact, in this type of apparatus, as the diver breathes, the oxygen of the mixture of gas under pressure is consumed and transformed into carbon dioxide which is retained by means of a purifying cartridge. The gas thus consumed is replaced by the gas under pressure which is expanded at ambient pressure when the diver inhales and produces a sufficient depression in the variable capacity chamber so as to enable the movable wall to activate the pressure reducer. The flow of gas from this pressure reducer should be controlled by the diver so that he can introduce only the quantity of gas which is required for the good progress of his dive. If the flow from the pressure reducer is too substantial, the quantity of gas which is introduced into the variable capacity chamber will be too great and will modify the floatability of the diver and of his apparatus.